Brands, marketers, agencies, rights holders and adtech platforms-(the demand side), have all clamored for more premium in-stream video inventory (supply side), or greater access to existing supply, though in 2016 the market is still defined by scarcity despite a proliferating device base.

In today's fragmented device universe marketers are buying what they know and what works: pre-roll formats on the desktop. There is buying momentum behind mobile/tablet/VOD inventory demand effectively moving the budgetary needle but not uniform across all devices.

The total market is forecast at $4.7 billion in 2016, and expected to increase at a moderate single digit rate through 2018; in-stream spend also remains constrained by measured demand (i.e. undersold inventory on emerging platforms).

While we estimate in-stream video inventory across all platforms/devices increased by 28.4% in 2015, spend actually declined by -5.6% due to higher levels of unsold/undersold inventory (i.e. mobile/tablet VOD) which contributed to lower average blended CPMs as more non desktop inventories flowed into publisher channels or private/public exchanges.

Insertion frequencies, on average, across all sites, networks and channels, increased in 2015 to 2.17, up 12% over 2014. Even so, after two years' worth of lackluster or even negative in-stream ad spending growth we expect the market to snap back to double-digit growth in 2016 with inventory increasing by 6% and spend by 42.6% as CPMs equalize and emerging platform inventory is more routinely fitted into media planners' digital video budgets.

Currently digital on-demand television (both brand extension and internet pure-play publisher content) is being monetized against broadcast ad loads across all platforms (i.e. ad insertions per number of video plays, or number of advertising minutes per programming hour/half-hour); the desktop remains the most exploited screen/platform, according to AvailPlay Video Monitoring Services by AccuStream Research.

A 30-minute show (22 minutes of runtime as defined by a linear television clock) has a range of 6 - 10 minutes of in-stream/online advertising, broken up into 3 - 4 pods, each pod with 1 - 7 ad units/avails of varying spot length.

A 60-minute show (43 minutes of runtime as defined by a linear television clock) has approximately 17+ minutes of in-stream advertising, broken up into 5 - 9 pods, each pod wit 1 - 7 ad units/avails of varying spot length.

Our research includes and concludes:

This research provides total views by publisher, insertion frequencies, total inventory (desktop, mobile/other), sellout, CPMs, historical, run rate and future year in-stream spend forecasts

VOD platforms deliver the most consistent content/ad playback experience, but on-demand services are the most immature and undersold at present

The desktop is the most exploited device type, and delivers a fairly consistent experience enhanced with audience/user information valuable to marketers

Android is a highly fragmented series of OS-powered platforms, which can result in inconsistent playback and inventory allocation

iOS benefits from some of the most sophisticated/supported apps

Non-desktop playback inconsistency and lack of deterministic audience profiling data are contributing factors leading to lower CPMs and undersold inventory

Allocation of in-stream inventory exhibits the characteristics of a sine curve, as increases have been followed by periods of lower total yield on the supply side

Despite the fact that in-stream inventory is relatively scarce, the emergence of new access points are typically undersold with brand ROI campaign buys based on formats/execution, consistency of playback, app design and competitive pricing

Including YouTube, in-stream video inventory is averaging a 2016 eCPM of $12.33 (eCPM is calculated as spend divided by all allocated inventory, including unsold/undersold plus TrueView skip formats). VOD is a premium ad avail, but the market is significantly undersold, and there are limited numbers of channels publishing for VOD.

As for YouTube, it's one of the top ad spend generating video-centric audience platforms online, both desktop and non-desktop. Inside partner channels, there is a combination of strategies with regard to insertion frequencies and TrueView/skippable inventory.

YouTube exploits Auto, Music, Comedy, Beauty/Fashion, How-to, and Cooking/Health with in-stream video inventory. The desktop, however, is by far the most exploited device type continuing into 4th Q. 2016 on the YouTube service.